Grinding mill



March 25, 1930. R. M., HARDGROVE GRINDING MILL Filed May 14, 1928 2 Sheets-Sheet l FIG 2.

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March 25, 1930. R. M. HARDGROVE 1,751,918

GRINDING MILL Filed May 14, 1928 2 Sheets-Sheet 2 NVENTO @Z%% Y M M ATTORNEY5.

Patented Mar. 25, 1930 UNITED STATES PATENT OFFICE LEHIGH GOMPANY, WARE OF FULLERTON, PENNSYLVANIA. A CORPORATION OF DELA- GRINDING MILL Application filed May 14, 1928. Serial No. 277,437.

This invention relates to a device for grinding or pulverizing particles of solid material such as lumps of coal, for example, by means of balls rolling along grinding surfaces. The

,, fine particles of material produced by the grinding operation may be removed by an air current or other means.

Heretofore it has been customaryto drive grinding balls in grinding mills of certain types by means of pressure or pusher arms that revolve around a central axis. In such (devices, the. tendency is for the balls to wear barrel-shaped, and the pressure arms also wear away rapidly. When the balls have 1 been worn to irregular shapes, they are apt to slide around upon the grinding surfaces, thereby causing the same to wear even more rapidly without grinding the material efliciently.

By the present invention, grinding balls are carried around by means of a rotating table, so that all parts of the surfaces of the balls come into contact with the table and grinding ring, thus causing the balls to wear evenly and also decreasing the amount of power necessary to drive the balls.

The invention will be understood from the description in connection with the accompanying drawings, in which Fig. 1 is a side view, partly in section, showing an illustrative embodiment of the-invention; Fig. 2 is a vertical. section on an enlarged scale," partly broken away, showing some of the details; Fig. 3 is a vertical section, partly broken away, showing a modification; Fig. 4 is a vertical section on an enlarged scale, partly broken away, showing some of the details of the modification, and taken along the line 4- 1 of Fig. 5; Fig. 5 is a plan view of Fig. 4; Fig. 6 is a vertical section on an enlarged scale, partly broken away, showing some of the details of a further modification; and Fig. 7 is a plan view of Fig. 6. i

In the drawings, reference character 1 indicates a grinding mill that is provided with a device 2 for feeding coal or other material into the mill to be ground. This feeder 2 may be driven by motor or in any other convenient manner, and may be regulated so as 50 to introduce the material into the mill at the proper rate. An air inlet 3 for forced air enters one side of the casing and the air therefrom-passesunder the lower edge of the baflie 4 and thence out through the outlet 5 at the top, picking up the fine particles of ground material and carrying them away.

A grinding ring 6 is provided near the bottom of the mill and is retained in place by means of the outside ring or holding member 7. The grinding balls 8 are rolled around in contact with the grinding ring 6 in the manner described below.

A vertical shaft 9 is provided at the lower end of the mill and is mounted in a bearing 10 on the spider 11 that is attached to the base 12 of the machine by bolts, or in any other convenient manner. A stufiing box or packing ring 13 surrounds the shaft 9 above the bearing 10 to prevent dust from entering the bearing. The upper end of the shaft 9 is made conical as shown at 14, to provide a seat for a ball supporting member or table 15 that is kept in place by means of the nut 16 on the shaft 9. The table 15 may be provided with a replaceable wearing ring 1 whose outer or ball contacting surface 18 may be hardened to withstand wear. Plows 19 may be attached to the edge of the table and extend into the space beneath the balls 8 to prevent the material from packing within this space.

A gear 20 is mounted on the shaft 9 be low the table 15 and drives the shaft. A' pinion 24 on the shaft 25 of the motor 26 drives the gear 20.

In the modification shown in Figs. 6 and 7, the balls 8 are shown as being of different sizes and the other parts are similar to those already described.

The operation is as follows: The material to be ground is fed into the machine by the feeder 2, and the air entering through the inlet 3 picks up and carries away the particles of ground material when they have been reduced to the proper degree of fineness. The turningof the table 15 by means of the shaft 9 being driven by the motor 26,

carries the balls 8 around, so that the balls roll upon the grinding surfaces of the rings 6 and 17 and grind the material by crushing the same between the balls and the rings. view of the fact that the balls 8 do not contact with the rings at diametrically opposite.

points, the balls keep turning to different positions, so that they wear evenly.

In the embodiment shown in Figs. 3, .4 and 5, the parts similar to those already. de-. scribed are designatedby the same reference characters, and the description thereof will not be repeated. In this embodiment,- the ring 6 is provided on its outside with a conically shaped portion which fits into acorresponding portion of the base 12 and keeps the ring in place. The table 15 isprovided with an upper conical surface 18 upon which the balls 8 rest, instead of resting upon a removable ring as described in connection with Figs. 1 and 2. In this embodiment, a loading ring 30 is provided having a beveled lower face 31 that rests uponthe balls to increase the grinding effect of the same.

In the modification shown in Figs. 6 and 7 the same general form of table and grinding ring as 15, 15 and 6, 6' are used, but the balls 8 instead of being all of the same diameter are of different diameters as better shown in Fig. 7 The advantage of this is to produce better grinding by having each successive ball trace a. different path of contact on each of the tables and the ring thereby doing more effective grinding and wearing the table and ring more evenly and prevents the format-ion of grooves. All of th balls will wear approximately the same,- so th t the smaller ones only need be removed after they have worn. to a certain diameter and they would be replaced by balls of thelargestdiameter. v I V The inside surfaces of the rings 6 and 6' are preferably made so as to slope downward- "ly and outwardly at a slight angle to the ver- I tical. It has been found that this angle to the also slopes downwardly and face 18' vertical may conveniently vary from about 5 to aboutf25. The upper grinding surof the table 15' (Fig. 4). or the grinding surface 18 of the ring 17 (Fig. 2), outwardly at an angle to thehorizontal, or at a larger angle to the vertical portion than the correspondmg surface of the outside grinding rings 6 'or 6, so that the balls 8 rest in a wedge-shaped space between the grinding ring and the table. It has been found in practice that the slope of the upper surface of the table in Fig.4, or corresponding ring'in Fig. 2, may

conveniently be from about ahorizontal plane to about to the horizontal. The best results are obtained when the included angle between the table and the grinding ring is between 30 to 40. The disposition of the grmdmg surface of the rings 6 or 6 as descrlbed above, causes the centrifugal force. on the balls 8 when they are driven to exert a pressure upon the tableand thereby increase e gnndmg effect of the balls.

Changes and modifications may be made without departing from the spirlt or scope of the invention.

1. In a grinding mill, a grinding ring having a grinding surface sloping downwardly I and outwardly, a member inside of said rin having a surface sloping downwardly an outwardly at a greater angle than the grinding surface of said ring, and balls between said ring and member. i

2., In a grinding mill, a' grinding ring hav- I ing a grinding surface sloping downwardly and outwardly, a revoluble member of smaller diameter than said ring having a surface sloping downwardly and outwardly at a greater angle than the grinding surface of said ring, and balls between said ring and member.

3. In a grinding mill, a grinding ring having a grinding surface sloping downwardly and outwardly, a revoluble member of smaller diameter than said ring havin' ing downwardly and outwardly at a greater angle than the grinding surface of said ring, said member being circular and coaxial with said ring, and balls between said ring and member. a

4. Ina grinding mill, a grinding ring haw ing a grinding surface sloping downwardly and outwardly, a revoluble member of smaller diameter than said ring having a surface sloping downwardly and outwardly at a greater.

a surface slopangle than the grinding surface of said ring,

said ring and member being revoluble and adjustable relative to each other, and balls between said r-ing and member 5. In a grinding mill, a grinding ring having a grinding surface sloping downwardly and outwardly, a revoluble member. of smaller diameter than saidring having a surface sloping downwardly and outwardly at a greater angle than the grinding surface'of said ring, means to vary the distance between said ring and member, and balls between said ringand member.

6. In a grinding mill, a horizontally d1sposed ball supporting table having a downwardly sloping surface, balls supported on said surface, a rin outside of saidsurface having asurface s oping downwardly in a more nearly vertical plane than the downwardly sloping surface of said table, and

means to revolve said table. f

7. In a grinding mill, a horizontally disposed ball' supporting table having a downwardly sloping surface, balls supported on saidsurface, a ring outside of said surface having a downwardly sloping surface, the downwardly sloping surfaces of said table and ring making an acute angle with each other, and means to revolve said table.

8. In a grinding mill, a circular-revoluble table, a grinding ring. and balls between said table and ring, said ring havingasurface to cause the centrifugalforce of said balls to exert pressure upon said table when it revolves.

9. In a grinding mill, a stationary grinding ring having, its grinding surface sloping downwardly and outwardly, a rotor having a downwardly and outwardly sloping surface,

' and a plurality of grinding balls between said surfaces resting against said rotor surface and driven thereby in contact with the grinding surface of said ring.

10. In a grinding mill, a horizontally disposed ball supporting table having a downwardly sloping surface, balls supported on said surface, a ring outside of said surface having a downwardly' slopingsurface, the angle between said downwardly sloping surfaces being between about 20 and 70, and means to revolve the table.

11. In a grinding mill, a horizontally disposed ball supportlng table having a downwardly'sloping surface, balls supported on said surface, a ring outside of said surface, havin a downwardly sloping surface, the angle etween said downwardly sloping surfaces being between about and 12. In a grinding mill, a stationary grinding ring having its grinding surface sloping downwardly and outwardly at an angle of about 15 to the vertical, a rotor havin a downwardly and outwar y surface slopin %about to the vertical, a

at an angle 0 plurality of grinding balls between said sur- .faces resting against said rotor surface and driven thereby in contact with the grinding surface of said ring. v

13. In a grinding mill, a grinding ring having a grinding surface slopin downwardly and outwardly, a member insi e of said rin having a surface sloping downwardly an outwardly at a greater angle than the grinding surface of said ring, and balls of different sizes between said rin andmember.

RALPH M. DGROVE. 

